1. Field of the Invention
The invention relates to a voltage converter, and particularly relates to a buck-type voltage converter capable of quickly stabilizing an output signal thereof.
2. Description of Related Art
Referring to FIG. 1, FIG. 1 is a circuit diagram of a conventional voltage converter. The conventional voltage converter 100 includes a gate controller 110, a ripple injection circuit 120, amplifiers OP1 and OP2, transistors M1 and M2, capacitors C1 and C2, resistors R1 and R2, and an inductor L1. The gate controller 110 periodically provides driving signals to control a turned-on or turned off state of the transistors M1 and M2, so as to generate an output signal VOUT.
Referring to FIG. 1 and FIG. 2, FIG. 2 is an operation waveform diagram of the gate controller 110 when a load state is changed. When the load state of the voltage converter 100 is changed (for example, changed from a light load to a heavy load), a load current ILOAD is switched from a low current value to a high current value. Correspondingly, voltage values of the output signal VOUT and a feedback signal VFB are decreased along with increase of the load current ILOAD. During such period, the ripple injection circuit 120 generates a ramp signal RAMP according to a magnitude of the feedback signal VFB, and provides the ramp signal RAMP plus the feedback signal VFB to the amplifiers OP1 and OP2, and the amplifier OP2 generates a comparison voltage COMP. The gate controller 110 controls the operation of generating the driving signal according to the comparison voltage COMP.
According to FIG. 2, it is clearly known that in the conventional voltage converter 100, a direct current (DC) component of the ramp signal RAMP is increased along with increasing of a current on the inductor L1 caused by reduction of the load current ILOAD, and a voltage of the feedback signal VFB is decreased along with decreasing of the load current ILOAD. Therefore, the signals (the ramp signal RAMP plus the feedback signal VFB) provided to the amplifiers OP1 and OP2 by the ripple injection circuit 120 do not include a state current reflecting a change of the load state, so that the comparison voltage COMP can't be adjusted in response to a large variation of the load state, which results in a fact that the voltage value of the output signal VOUT is greatly decreased.